Internal combustion engines, like reciprocating engines used in automobiles, normally use intake valves to control admission of air or air-fuel-mixture into the engine cylinders, and exhaust valves to let exhaust gases out of the cylinders. Each cylinder commonly has one or more intake valves and one or more exhaust valves. Various systems have been developed for controlling these engine valves to improve fuel economy and performance. For instance, variable valve timing systems can control the opening and closing of the intake and exhaust valves while the engine is operating, and cylinder deactivation systems can turn-off at least some of the engine's cylinders when the vehicle is under certain operating conditions.